A boring president, awfully mundane (10)
I believe the answer is:
Here is my best explanation:
'mundane' is the definition.
'a boring president awfully' is the subsidiary indication.
'boring' is an insertion indicator (some letters must \'bore\' a hole into other lette).
'awfully' is an anagram indicator.
'president' is an anagram of 'pedestrin'.
'a' going within 'pedestrin' is 'pedestrian'.
(Other definitions for pedestrian that I've seen before include "Person walking", "Unimaginative", "Walker; prosaic", "Prosaic; walker", "Dull, uninspired", "Boring", "Unexciting" and "Dull; walker".)